The present invention relates to a new process for the production of substituted anthraquinones which are used as synthesis intermediaries, notably for the production of hydrogen peroxide and the synthesis of dyes.
It is known to produce substituted anthraquinones by dehydrating the corresponding benzylbenzoic acids using oleum (U.S. Pat. No. 3,032,560 filed on May 29, 1959 in the name of L. H. Dawsey). These processes require the use of large quantities of oleum, which leads to the formation of residual sulphuric acid contaminated by organic substances which is very difficult to recover.
There have also been attempts to prepare unsubstituted anthraquinone by a direct reaction between phthaloyl chloride and benzene (C. Friedel and J. M. Crafts, Ann. Chim. Phys., 1884, (6), 1, page 5230). The main product of this reaction is, however, a phenylphthalide, anthraquinone being produced only in traces.